Dual Light Emission of CsSnI3-Based Powders Synthesized via a Mechanochemical Process.

Lead toxicity has hindered the wide applications of lead halide perovskites in optoelectronics and bioimaging. A significant amount of effort has been made to synthesize lead-free halide perovskites as alternatives to lead halide perovskites. In this work, we demonstrate the feasibility of synthesizing CsSnI3-based powders mechanochemically with dual light emissions under ambient conditions from CsI and SnI2 powders. The formed CsSnI3-based powders are divided into CsSnI3-dominated powders and CsSnI3-contained powders. Under the excitation of ultraviolet light of 365 nm in wavelength, the CsSnI3-dominated powders emit green light with a wavelength centered at 540 nm, and the CsSnI3-contained powders emit orange light with a wavelength centered at 608 nm. Both the CsSnI3-dominated and CsSnI3-contained powders exhibit infrared emission with the peak emission wavelengths centered at 916 nm and 925 nm, respectively, under a laser of 785 nm in wavelength. From the absorbance spectra, we obtain bandgaps of 2.32 eV and 2.08 eV for the CsSnI3-dominated and CsSnI3-contained powders, respectively. The CsSnI3-contained powders exhibit the characteristics of thermal quenching and photoelectrical response under white light.

Ultra-stable blue-emitting lead-free double perovskite Cs2SnCl6 nanocrystals enabled by an aqueous synthesis on a microfluidic platform.

Blue emitting Sn-based lead-free halide perovskite nanocrystals (NCs) are considered to be a promising material in lighting and displays. However, industrialised fabrication of blue-emitting NCs still remains a significant challenge due to the use of toxic solvents and optical instability, not mentioning in large-scale synthesis. In this work, a green-route synthesis of blue-emitting lead-free halide perovskite Cs2SnCl6 powders is developed, in which deionized water with a small amount of inorganic acid is used as the solvent and the synthesis of the Cs2SnCl6 powders is achieved on a microfluidic platform. Using the Cs2SnCl6 powders, we prepare Cs2SnCl6 NCs via an ultrasonication process. Changing the volume ratio of the ligands (oleic acid to oleylamine) can alter the photoluminescence (PL) characteristics of the prepared NCs, including the PL-peak wavelength, PL-peak intensity and quantum yield. The highest photoluminescence quantum yield (PLQY) of 13.4% is achieved by the Cs2SnCl6 NCs prepared with the volume ratio of oleic acid to oleylamine of 40 µL to 10 µL. A long-term PL stability test demonstrates that the as-synthesized Cs2SnCl6 NCs can retain a stable PLQY over a period of 60 days. This work opens up a new path for a large-scale green-route synthesis of blue-emitting Sn-based lead-free NCs, such as Cs2SnX6 (Cl, Br and I), towards their applications in optoelectronics.

MAPbBr3nanocrystals from aqueous solution for poly(methyl methacrylate)-MAPbBr3nanocrystal films with compression-resistant photoluminescence.

In this work, we develop an environmental-friendly approach to produce organic-inorganic hybrid MAPbBr3(MA = CH3NH3) perovskite nanocrystals (PeNCs) and PMMA-MAPbBr3NC films with excellent compression-resistant PL characteristics. Deionized water is used as the solvent to synthesize MAPbBr3powder instead of conventionally-used hazardous organic solvents. The MAPbBr3PeNCs derived from the MAPbBr3powder exhibit a high photoluminescence quantum yield (PLQY) of 93.86%. Poly(methyl methacrylate) (PMMA)-MAPbBr3NC films made from the MAPbBr3PeNCs retain ∼97% and ∼91% of initial PL intensity after 720 h aging in ambient environment at 50 °C and 70 °C, respectively. The PMMA-MAPbBr3NC films also exhibit compression-resistant photoluminescent characteristics in contrast to the PMMA-CsPbBr3NC films under a compressive stress of 1.6 MPa. The PMMA-MAPbBr3NC film integrated with a red emissive film and a blue light emitting source achieves an LCD backlight of ∼114% color gamut of National Television System Committee (NTSC) 1953 standard.

Local Deformation and Texture of Cold-Rolled AA6061 Aluminum Alloy.

Using cold rolling, we plastically deform AA6061 sheets at room temperature and investigate the variations of the microstructures, textures and local deformation of the cold-rolled AA6061 sheets as functions of thickness reduction (Δt/t0, t0 and t are the thicknesses of the AA6061 sheet before and after the cold rolling, respectively). The volume fraction of total deformation texture is relatively independent of the thickness reduction for Δt/t0 ≤ 30%, and becomes an approximately linearly increasing function of the thickness reduction for Δt/t0 > 30%. Increasing the thickness reduction causes the increase of the Vickers hardness of the cross-section of the cold-rolled sheets, which exhibits a similar increase trend to the volume fraction of total deformation texture for Δt/t0 > 30%. A simple relation between the Vickers hardness and the thickness reduction is established and is used to curve-fit the experimental results.